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Evidence for the benefits of meditation in fighting age-related cognitive decline

Submitted by Fiona McPherson on Mon, 02/09/2015 - 20:54

A review of meditation research reported in January last year concluded that there were insufficient good studies to allow us to say that meditation clearly improves attention and cognition. Studies from 2014 suggest three factors that might be part of the reason for inconsistent research findings:

the age of the subjects (with benefits being more evident in older participants)

the cognitive tests used (some may be insufficiently demanding to reveal effects, especially in younger adults)

the type of meditation (meditative practices that increase arousal may be more beneficial than those that encourage relaxation).

Of course, there are other potentially significant factors as well, such as the meditation experience of the participants. What we really need is a more methodical research program. Nevertheless, the results are promising.

Review of meditation research

At the beginning of last year, a very large review of the meditation research by the US Agency for Healthcare Research and Quality (AHRQ) came out, and concluded that while meditation, and mindfulness meditation in particular, helps reduce stress and some other negative factors, the quality and quantity of studies to date means that we should be cautious of drawing too many conclusions as regards type of meditation, the groups of people who might benefit, and specific benefits.

So, for example, while MBSR appears to help with musculoskeletal pain, almost no other types of pain have been studied, and we cannot therefore conclude that any other types of pain will be alleviated.

The study reviewed 47 clinical trials from 2012 that evaluated the effects of meditation on individuals with diagnosed health problems. These represent a mere 3% of the meditation studies published that year, being those that met the stringent criteria:

subjects randomly assigned to a mediation or control group

control condition to require a similar amount of time and focus as meditation

whether the researchers knew what intervention they had received

They found moderate evidence that mindfulness meditation alleviates pain, anxiety and depression (the latter two to a similar degree as antidepressant drug therapy), but found low evidence of no effect or insufficient evidence of any effect of meditation programs on mood or attention. Nor could they find sufficient evidence for the benefits of other types of meditation. They also found no evidence that meditation programs were better than any active treatment (drugs, exercise, or other behavioral therapies).

The researchers made it clear that the problem lies in a paucity of good studies, and hoped that their findings would encourage better quality research.

Here are some of the 2014 studies suggesting cognitive benefits. These suggest several reasons why research findings may have been inconsistent.

Meditation slows age-related loss of gray matter

Following an earlier study that suggested people who meditate have less age-related atrophy in their white matter, a new study has found that meditation also appears to help preserve gray matter.

The study compared 50 experienced mediatators against 50 age- and gender-matched controls. Each group contained 28 men and 22 women ranging in age from 24 to 77. Those who meditated had been doing so for four to 46 years, with an average of 20 years.

While both groups showed a loss of gray matter as they aged, the decline was significantly less in those who meditated. Moreover, the loss of gray matter was more widespread among those who didn't meditate, including several regions previously implicated in meditation effects.

Interestingly, a 2007 study found a smaller difference between their controls and meditators, as well as a more localized effect (only one region, the putamen, showed a significant difference in gray matter, compared to this study's finding of nine significant clusters across the brain). It's plausibly suggested that the difference may lie in the average age of the subjects: the average age in the earlier study was in the mid-thirties, while the average in this recent study was in the early-fifties.

In other words, the benefits of meditation for cognition may be better seen as we get older.

Yoga and meditation produce better brainwaves

Another, related, reason for meditation to produce inconsistent or small cognitive benefits is that the cognitive testing is insufficiently demanding. A recent study has found that those who practiced yoga and meditation long term learned to control a computer with their minds faster and better than people with little or no yoga or meditation experience.

The study involved 36 participants, of whom 12 had at least one year of experience in yoga or meditation at least twice a week for one hour. Participants were given three, two-hour training sessions with a human-computer interface, in which they had to try to move a computer cursor across the screen by visualizing left or right hand movements.

The participants with yoga or meditation experience were twice as likely to complete the brain-computer interface task by the end of 30 trials and learned three times faster than their counterparts for the left-right cursor movement experiments.

There has been much in the news in recent years about these interfaces, which allow a person to control a computer or robot with their minds, and offer such promise for people who are paralyzed. However, it turns out that not everyone can easily learn to use the interface, and it's been speculated that the problem may lie in the clarity and steadiness of the brain signal. Meditators have shown more distinctive EEG patterns than untrained participants, which may explain their success.

Hatha yoga boosts brain function in older adults

Yoga has also been shown to help executive function in older adults.

A study involving 108 sedentary older adults (55-79), of whom 61 attended hatha yoga classes three times a week for eight weeks, found that the yoga practice improved their cognitive performance, compared to those who spent the same time engaged in stretching and toning exercises.

At the end of the eight weeks, the yoga group was faster and more accurate on task switching and working memory capacity tests. There was no change in performance for those in the stretching group.

Some meditation practices are better than others

A third reason for inconsistency may come from the fact that meditation comes in many flavors. Are they all equally helpful? Two studies in 2014 gave us some pointers.

The first study distinguished two main types of meditation technique:

concentrative meditation, where the meditator focuses attention on their breathing or on specific thoughts, thus suppressing other thoughts

nondirective meditation, where the meditator focuses on their breathing or a meditation sound, but allows the mind to wander freely.

In this study, 14 meditators skilled in a nondirective technique called Acem meditation had their brains scanned while resting or performing nondirective meditation or a more concentrative meditation task. Surprisingly, nondirective meditation led to higher activity in the right medial temporal lobe (parahippocampalgyrus and amygdala) — areas associated with attention, mind wandering, retrieval of episodic memories, and emotional processing — while the level of brain activity in this region when the meditators performed concentrative meditation was about the same as during rest.

The results suggest that nondirective meditation produces more extensive activation of the default mode network. This finding contrasts with other studies that have indicated meditation reduces activity in the default mode network.

Which should we believe? Well, the second study compared four different types of meditative practices (two types of Vajrayana meditation practices (visualization of self-generation-as-Deity and Rig-pa) and two types of Theravada practices (Shamatha and Vipassana)). This distinction cuts across the previous distinction. Shamatha (Theravada) and self-generation-as-Deity (Varjrayana) are examples of focused attention / concentrative meditation. Vipassana (Theravada) and Rig-pa (Vajrayana) have been classified as non-focused / nondirective. These researchers argue that this broad distinction is not a particularly accurate or helpful one, pointing to the inconsistent findings regarding whether focused and non-focused meditation show clearly distinct neurophysiological substrates. Their findings support this view (although of course it's easy to be consistent with one study! more research is clearly needed).

The study found that physiological responses during the Theravada meditation differed significantly from those during the Vajrayana meditation, with Theravada meditation producing enhanced parasympathetic activation (relaxation), while Vajrayana meditation didn't show any evidence of parasympathetic activity but showed an activation of the sympathetic system (arousal).

Arousal is more likely to be associated with attention, and indeed, cognitive performance improved (immediately and dramatically) only following the Vajrayana styles of meditation. This was shown in a mental rotation test and a visual memory test.

In other words, to deal with stress and become more relaxed, you should choose a Theravada meditation, but if your desire is to improve your powers of concentration, you should practice a Vajrayana meditation. Note however, that this study looked only at the immediate alertness following meditation — whether experienced Vajrayana meditators are at an advantage in general is a separate issue.